Especially for aneurysm treatment, but also for either one of the aforementioned treatments, the form of the ball is very important. In particular, the density of the device is paramount in applications where braid itself is intended to moderate or stop blood flow—allowing thrombosis within a volume formed by the ball.
According to the present invention, braid-ball type implants are provided in braid of sufficient density is provided to moderate blood flow within the volume of the implant. Upon thrombosis, flow thereto is stopped. Alternatively, a blood-barrier covering can be applied to the filamentary structure to immediately stop blood flow into the vascular site, in which the implant volume is set.
In either case, to form thrombosis within the volume of the ball, the filaments of the braid matrix permit filling of the implant with blood when emplaced at a vascular treatment site. This blood then thromboses due to the flow-disruption effect(s).
Unlike Nitinol tube-cut cages that may be suitable for (or assist) in coil retention, the ball devices are adapted to work alone—or in combination with each other to effect a complete treatment. As such, high density braid/mesh is typically required. Namely, braid having at least about 48 ends, typically set at about 90 degrees or greater, in diameters from about 4 to about 8 mm may be employed. At larger diameters (e.g., about 6 to 12 or more), more wire ends (e.g., 64, 72 and upwards) may be employed in forming the balls.
Suitable braid for constructing the balls may be obtained from Secant Medical, Inc. Wire diameters may be in the range of about 0.001 to about 0.003 inches, depending on desired delivery profile (which is typically less than about 0.050 inches). The braid forming the balls may incorporate only one size wire, or may be formed with multiple sizes.
The wire is preferably superelastic NiTi alloy. The metal may be a binary alloy or a ternary alloy to provide additional radiopacity. Alternatively, radiopaque platinum fibers may be included in the braid, or the wire may comprise platinum or gold cord Nitinol DFT. Otherwise, wraps or bands (preferably Pt) used to secure the braid wire may serve as the sole radiopaque feature(s).
In any case, the construction approaches described herein enable producing these useful devices. Whether comprising braid alone, or incorporating some further blood-barrier covering (such as a thin urethane film as may be applied by Hantel, Inc. or others) the use of braid presents numerous challenges in managing the termination of multiple wires and in forming the desired structures.
Also included in the invention are detachable implant pushers that utilize a resistance wire heater to thermally sever a suture associated with the implant to effect release. As distinguished from known approaches where an implant is retained by a loop connected back to a delivery system pusher that is withdrawn with the devilry system, the present invention contemplates a leave-behind tether.
Further details, variations, modification and optional features of the invention may be appreciated by review of any of the incorporated patent applications. However, the priority date and subject matter included in the appended claims rely solely on the subject matter filed in U.S. Provisional Patent Application Nos. 61/046,670 and 61/046,594, the earliest patent applications (each filed Apr. 21, 2008) one which U.S. patent application Ser. No. 12/427,620 relies. Selected figures from the '670 and '594 application and all of text from the '594 application—all—incorporated by reference in the parent application hereto is reproduced herein.